Oscillating belt sanders



5 Sheets-Sheet l INVENTOR. Edward S. Somme":

BY I 2 fi March 1, 1960 E s soMMERs OSCILLATING BELT SANDERS Filed Sept. 5. 1957 March 1, 1960 E. s. soMMERs OSCILLATING BELT SANDERS 5 Sheets-Sheet 2 Filed Sept. 5, 1957 llll llll rlllvl INVENTOR.

Edward 5. 50mm era March 1, 1960 E. s. SOMMERS 2,926,465

OSCILLATING BELT SANDERS Filed Sept. 5, 1957 5 Sheets-Sheet 3 IO INVENTOR.

Edmund J. \some s E. S. SOMMERS OSCILLATING vBELT SANDERS March 1, 1960 5 Sheets-Sheet 4 Filed Sept. 5, 1957 INVENTOR. fl u/ard J fommers March 1, 1960 E. s. SOMMERS 2,926,465

OSCILLATING BELT SANDERS Filed Sept. 5, 1957 I 5 Shee"cs-Sheet 5 INVENT OR.

Eda/4rd J Jmmers United States Patent O OSCILLATING BELT SANDERS Edward S. Summers, Chicago, Ill.

Application September 5, 1957, Serial No. 682,249 5 Claims. (Cl. 51-142) My invention herein pertains to continuous belt machines which grind or polish a work piece either in a horizontal or in angular planes. More particularly my device relates to a sanding machine in which the means rotatively mounting the abrasive elements reciprocate axially for example in a horizontal or transverse plane. The transverse oscillation of such mechanism is one basic characteristic and advantageous feature of the invention as oscillation keeps the belt clean, avoids clogging and produces clean work.- i

While certain machines have been devised for driving a rotatably mounted beltthaving abrasive surface thereon with the working abrasive face of the belt in a vertical plane, and in which the mounting means has been slidably mounted, such previous machines are not adaptable or suitable for preparing horizontal and rounded surfaces of numerous products and work elements. For example, in the art of preparing the edge faces and rounded corners of books preliminary to application of gold or other metallic gilding, in which the plurality of paper pages are tightly clamped under pressure, it is necessary that the edge faces of the book held within opposed metal clamps be carefully and perfectly sanded to present a very straight, even, unscratehed and undamaged surface in order that the very thin gold or metallic leaves applied and secured thereto will properly adhere to the edges of each and every page or sheet of the book, and present no recesses, scratches, or dents.

In the preparation of book edges for gilding, one edge face of the book at a time is necessarily positioned horizontally and facing upwardly. The rounded corners have to be separately sanded and prepared. Accordingly, the

moving and/or rotating abrasive belt, must, along with its mounting means, be adjustably mounted so as to permit selective manual downward and upward movement and selective angular movement of the belt into selective engagement with the upwardly exposed edge face or the J corner faces of the books. Further, it is important. that clogging and filling of the abrasive belt be avoided and it has been found that rotative movement in a straight path of such abrasive belts in engagement with the edges of books results in quickly filling, clogging and loading of the sand belt by the small fibrous particles removed from the book and page edges.

By repeated experimentation I have found that transverse and intermittent reciprocation or oscillation of the driven abrasive belt, which avoids continuous travelling Patented Mar. 1, 1960 mentary stoppage of movement of the book or work, while in engagement with the abrasive travelling belt, causes a dig-in or shallow recess'which ruins the edge face from the standpoint of a commercially acceptable gilding application.

It is, accordingly, one of the objects of my invention to provide an oscillating sanding machine having means and mechanism for rotatably mounting and driving an endless abrasive belt and also having novel means for reciprocating and oscillating the shaft and roller means on which the endless abrasive belt is mounted so as to' produce more even and smooth surfaces or faces which will not have any scratches, recesses, cavities, or damaged edges, and which will avoid burning of the work pieces or of the surfaces of book edges or the like due to friction and heat.

It is a further object and accomplishment of my invention to provide a sanding machine with novel mechanism providing for horizontal oscillation of the abrading beltsand its mounting means, so as to produce more even and smooth surfaces on the work, and which is capable of being run at relatively slow or at any desired speeds, and in which include means adjustably positioning the work head at different angles in relation to various work hav-.' ing rounded or angular faces to be abraded, and which includes novel means for mounting different workheads in varying positions without the necessity of changing the mechanism for the horizontal oscillation.

A further object of my invention is the provision of a projecting reciprocable head in a sanding machine having a means for maintaining an even and cushioned support for the lower flight of an endless abrasive belt against which the work is selectively pressed, and which is free from any obstructing adjacent parts which would hinder the free movement of the work below or along the abrasive belt.

Other and further objects of my invention will be apparent from the following description and appended claims.

On the drawings:

Fig. l is a top plan view of one preferred embodiment of my oscillatable sanding and abrasivedevice.

Fig. 2 is an enlarged top plan view, with parts broken away, of a belt mounting head and adjacent parts, and illustrating the connections to the reciprocating mechaniSm as broken away.

Fig. 3 is a side elevation taken substantially on a vertical plane, indicated by line 33 of Fig. 2.

Fig. 4 is an enlarged cross sectional view of portions of the reciprocating shafts and connecting bar and taken substantially on a vertical plane, indicated by line 4-4 of Fig. 1.

Fig. 5 is an enlarged elevation of one of the bearing mounting hangers or brackets, illustrating portions of the shaft and base broken away, and taken substantially on line 55 of Fig. 1. 1

Fig. 6 is an enlarged partially cross' sectional and partially elevational view of one of the bearing hangers or brackets and taken substantially on a vertical plane, indicated by lines 66 of Fig. 1.

Fig. 7 is a perspective View, with parts broken away, illustrating one of various angular positions in which the carrying head and attached parts may be angularly mounted.

Fig. 8 is a perspective view, with parts broken away, illustrating a modified form of the mounting head of my invention employing a single abrasive wheel.

Fig. 9 is an enlarged cross sectional view of a horizontal plane taken substantially through the central portion of Fig. 8, as indicated by line 99 thereon and illustrating the connection of the shaft to the driving means.

Referring to Fig. 1, numeral designates a metal base or base plate which may vary in shape, though which is illustrated as substantially rectangular. Securely mounted on the base 10 by bolts or screws 9 are two pairs of spaced apart journalling and bearing brackets or hangers 11 and 12. The two passaged brackets 11 are longitudinally aligned and the two brackets 12 are positioned in alignment at the right of Fig. 1. Numerals 13 designate oil cups mounted in openings (not shown) through which lubricant is fed to the respective bearings.

Numeral 14 designates a reciprocal bar or shaft which is slidably mounted in bearing hangers 11, and numerals 15 designate a bar or shaft slidably mounted in the bearings of hangers 12. The ends of shafts 14 and .15 extend beyond the edge of the base 10, as illustrated at the upper portion of Fig. 1.

A plurality of metal collars 4 are mounted on all four projecting ends of the two slidable shafts 14 and 15, one of said collars 4 being positioned at each end of each bearing of the heads of hangers 11. Each of said collars are suitably mounted on the respective ends of the heads of hangers 11 by press fit or threading or equivalent securance.

Expanded compressible springs 3 are mounted on the projecting end portions of the two shafts 14 and 15 with one end of each of said springs engaging the respective adjacent collars 4. Washers 5 are mounted on the end portions of shafts 14 and 15 and normally bear against these springs 3, respectively. The end portions of said shafts 14 and 15 have diametrical holes formed therein adjacent to the positions of said washers 5, and retaining or anchoring pins 6 are mounted in said holes respectively to bear against the respective washers 5 and thereby maintaining the respective springs 3 under tension.

A metal cross bar 16 having transversely passaged end portions, as illustrated, is mounted to rigidly connect together the intermediate portions of shafts 14 and 15, as illustrated in Fig. 1. The opposite passaged end portions of connecting bar 16 have threaded holes therein in which are threaded suitable tightening and securing bolts 17. The intermediate portion of bar 16 has a passaged hub 18.

An intermediate metal guide bar 19 is mounted to extend through hub 18 and through the two spaced apart passaged heads of aligned journalled brackets or hangers 20 and 21 whose lower base portions are suitably secured to the base plate 10 by bolts 20a, as shown in Fig. 6. Suitable thrust collars 22 are secured on guide rod 19 on opposite sides of hub 13, and similar metal collars are mounted on the shafts 14 and 15 on opposite sides of the passaged end portions of connecting bar 16, as illustrated in Fig. 1. Two metal collars 4 are threadingly mounted on opposite ends of hanger 21 as illustrated in Fig. 1.

Referring to Fig. l, numeral 23 designates a prime mover in the form of an electric motor. It is suitably secured on base 10 adjacent one corner portion thereof, for example by bolts (not shown). The shaft 24 of motor 23 has a suitable pulley 24a mounted thereon in a plane common to the planes of shafts 14 and 15. Numeral 25 designates a pair of journalling or pillow blocks or brackets shown at the lower part of Fig. l, in which a shaft 26 is journalled. Shaft 26 carries a pulley 27 on one end to which pulley 37 is drivingly connected by an endless belt 28 to the pulley 24a driven by said motor.

The opposite end of shaft 26 carries an eccentric or cam pulley 29. The metal link or connecting bar 30 has one end thereof connected on the eccentric member 29 and its other end pivotally connected to the bifurcated projecting end portion of shaft 19 by means of pin 31, as illustrated in Fig. 1. It will be understood that the motor actuated movement of the movable parts described will produce reciprocation and oscillation of the guide rod 19, cross bar 16 and shafts 14 and 15.

The outer end portions of the shafts 14 and 15 have suitably secured thereon, for example by threading engagement, a pair of apertured mounting collars 32. The outer end of guide bar 19 also has suitably secured thereon an apertured collar 33.

In the preferred form of my invention, as illustrated in Fig. l, the mounting head which mounts and carries the movable abrasive element is adapted to be connected to the movable collars or apertured flanges 32 by suitable securing means, for example by bolts 34 which extend through apertures formed in portions of said collars.

As illustrated in Fig. 1, numeral 35 designates an electric motor of suitable capacity which is connected by circuit wires (not shown), to an electric power source. Motor 35 has its base suitably secured by bolts (not shown) to the base i in a position substantially adjacent one edge portion of said base. Electric motor 35 has a suitable manually operable control switch 38, the outer portion of which is illustrated at the lower right of Fig. 1. Motor 35 has a projecting shaft 36 on which is mounted a suitable removable coupling 37. Numeral 39 designates a flexible shaft having one end connected in a conventional manner to the coupling 37 and its other end is connected to one portion of flexible coupling 40, shown at the upper right of Fig. 1. Flexible coupling 40 is normally connected to the driven shaft of a driving pulley or roller hereinafter described.

The outer mounting flanges 32 are centrally apertured and threaded and threadingly mounted on the outer ends of the shafts 14 and 15 and on the end of guide bar 19, as illustrated in Figs. 1 and 2.

Referring to Figs. 1 and 2, numeral 41 designates a rigid elongated apertured metal mounting plate which has a plurality of spaced apart apertures 45 therein, a part of which apertures are located at points corresponding to the positions of the respective apertures in the mounting flanges or collars 32. In Fig. 2, a plurality of suitably spaced apart passages or holes 45 are illustrated as extending through the mounting plate 41 and through the flange of shoe 42, which provide for varying angular mounting of the head and parts carried thereby, by means of two or more of the bolts 43. In changing the relative position of the head and abrasive belt, the bolts 43 are removed, and two or more of said bolts 43 are then inserted in certain of the passages 45 which are so located as to change the plane and position of said head. As shown at the left of Fig. 2, plate 41 has a longitudinally extending slot 57 through which the shaft 56 extends, and this provides for adjusting the position of said shaft as hereinafter described.

I have illustrated in Figure 3, inside elevation of the shoe 42, looking at the lateral free edges of the said shoe 42, and wherein said shoe is of channel-like shape and having a second flat flange forming an upper integral shoe 42a. A second and upper yieldable cushion 44a, is secured on the upper fiat face of the said second shoe 42a, for example, by suitable adhesive cement (not shown).

As shown in the upper portion of Figure 1 and in Figures 2 and 3, a metal shoe plate or backing plate 41 of elongated right angle cross section has its narrower flange portion suitably perforated with a plurality of holes in positions to correspond to the positions of certain of the holes in the mounting bushings 32 and 33, respectively.

The main angular portion of said metal shoe extends outwardly and normally horizontally and is disposed in a position to normally lie adjacent and above the lower fiight of an abrasive belt, as illustrated in Fig. 3. A plurality of bolts 43 are mounted in and extend through the respective holes in the flange of shoe 42, of mounting plate 41 and of mounting bushings 32 and 33, respectively, on which suitable nuts are secured to thereby mount and hold the mounting plate 41 in a plane perpendicular to the longitudinal axis Of the Shafts 14 nd 15, and to thereby hold Y of the driven abrasive belt.

the outwardly extending flat portion of the shoe 42 in a plane parallel to the plane of the shafts 14 and 15.

As illustrated in Fig. 3, a yieldable flat cushion 44 is secured, preferably by suitable cement, to the lower flat face of the shoe 42 so that the outer face of said yieldable cushion 44 will be normally slidably engaged by a flight While I have illustrated said mounting head, said shoe 42 and said cushion 44 in Fig. 3 as positioned to engage the normally upper faces of articles for work to be abraded, I desire it to be understood that the position of said head and of the parts carried thereby may be varied, for example, the mounting plate 41 removed and its position reversed so that the shoe plate 42 and its cushion 44 will slidingly support the upper flight of a driven abrasive belt. Similarly, I desire it to be understood that by removing the entire head, by removal of the bolts 43, the said head may be mounted in angular and inclined positions in relation to the reciprocating mechanism and its base, this by positioning the mounting plate 41, which has formed therein additional and variously spaced holes 45, to any one or two of the mounting flanges 33 or 32. Such angular positioning of the head and angular and inclined travel of the driven belt is highly desirable in preparing certain types of work facings, for example, rounded corners, abutments, etc.

As illustrated in Figs. 1, 2 and 3, the reciprocable mounting head has secured thereon a metal plate 46 which is suitably secured in the inside face of the shoe 42. Said plate 46 has secured thereto a metal sleeve or cylinder 47 in which is mounted a compressible spring 48. An adjustable metal externally threaded shaft 49 has its free end portion enlarged, as illustrated in Figs. 2 and 3, and slidably mounted within sleeve or cylinder 47 and in engagement with one end of spring 48. Said shaft 49 has its intermediate portion externallythreaded, as illustrated in Figs. 2 and 3, and extending through the offset middle portion of an apertured metal bracket 50 whose opposite apertured end portions are secured by a pair of bolts 51 to the transversely extending portion of the shoe 42, in which suitably located bolts for said holes are formed. A transversely extending centrally passaged metal plate 52 has its normally lower edge secured to shoe 42 in a position adjacent to bracket 50.

An adjustable lock nut 53 is threaded on a threaded portion of shaft 49 to engage one edge portion of bracket 50, and a second adjustable lock nut 54 is threaded on shaft 49 to engage and bear against one face of the plate 52, as illustrated in Figs. 2 and 3. Mounted on the end portion of ,the shaft 49 is a metal fork or yoke 55 whose arms have aligned passages therethrough to provide bearing means for a driven shaft which is designated bynumeral 56. Driven shaft 56 has its outer end extending loosely and suitably through a longitudinally extending slot 57 formed in the end portion of mounting plate 41. The outer end of said shaft 56 is connected to one end portion of a flexible coupling 40, as illustrated in the upper portion of Fig. l. Said'driven shaft 56 is journalled in the two aligned passages of the arms of yoke 55, as shown in Figs. 1 and 2. A pair of suitable washers 59and pins 58 are mounted on the opposite end of shaft 56 to aid in maintaining said shaft 56against longitudinal movement, and said washers 59 normally engage the outer faces of the two legs respectively of the yoke 55.

r A cylindrical pulley or roller 60 is securely mounted on the driven shaft 56 between the arms of the yoke 55 so that said pulley will always rotate with and on said shaft 56.

As shown at the upper right portion of Fig. 2, the mounting plate 41 carries an integral apertured ear 61 on which is pivotally mounted a shaft or spindle 62 by means of a pin or pivot 63. The shaft 62 extends substantially beyond the outer edge of the shoe 42 and carries a recessed socket 64, as shown in Fig. 2. Secured on the outer edge portion of the shoe 42, by welding or the like, is a metal projecting ear or lug 65 whose outer end portion is sew threaded and apertured, as shown in Fig. 2. A manually operable adjusting screw 66 is threaded in the threaded opening of ear 65 and its end portion is reduced and formed into a substantially ball-shaped end which is rotatably mounted in the recess of socket 64.

Suitably journalled on the shaft 62 is an idler pulley or drum 67 which is normally maintained against longitudi-J nal movement on said shaft 62 by pins 68 extending diametrically through shaft 62. Numeral 69 designates a conventional abrasive belt which is mounted about the pulleys 60 and 67, said belt being shown in cross section in Fig. 2 and in side elevation in Fig. 3.

It will be understood that when an endless belt is removed and a new belt mounted on said pulleys, the screw 66 will be released to thereby move the idler pulley closer to the driven pulley 60 to thereby remove the tension of .the belt and permit it to he slipped off over the ends of the pulleys. Similarly, a new belt may be mounted thereon and thereafter the screw 66 is rotated to pivot and move the shaft 62 outwardly and away from pulley 60 to produce the desired tension on the endless belt.

In Fig. 7, l have illustrated a perspective view of the previously described adjustable pulley and belt mounting head which mounts the abrasive belt as described and which is illustrated in an angular or inclined position in relation to the mounting plate 41. The mounting plate 41 is shown as broken off, and it is connected in the previously described manner by bolts or screws to the connecting collars or brackets 22, said collars being illus: trated by dotted lines in Fig. 7. Said collars 22 are connected to the ends of slidable shafts 14 and 15 (one of which is shown in Fig. 7) and to the slidable guide bar 19, as previously described.

Referring to Figs. 1, 2, and 7, it will be noted that the plurality of spaced apart holes 45, formed in mounting plate 41, provide for releasably and adjustably securing in relative angular position, the shoe plate 42a to mounting plate 41 by means of suitable bolts 70, two of which are illustrated in the upper portion of Fig. 7, said bolts being mounted in desired holes 45 in plate 41 and in correspondingly spacedholes 71 in said mounting shoe. The driven shaft 56, on which the driven pulley 60 is mounted, is illustrated as having the aforesaid described coupling connected thereon through which the driving force is transmitted from the driven flexible shaft.

It is highly advantageous in certain types of work, for example in sanding and smoothing corners or rounded corners or beveled faces of various articles to have the endless abrasive belt run in an inclined position, as this permits proper and correct engagement of such faces of articles to be pressed into engagement with the lower flight of the abrasive belt 69.

In Figures 8 and 9, I have illustrated a modified form of adjustable head, with a portion of the mounting plate 41 broken away, and having a single abrasive wheel 76 mounted on the driven. shaft 75 with its threaded end having a threaded nut 78.

The reciprocably mounted oscillating plate 41 has a suitable aperture therein in which is mounted a conventional roller bearing 73, as illustrated in Fig. 9. Said bearing (73) is suitably mounted in said aperture (no-t shown) in end portion of mounting plate 41 and held in position by a pair of metal collars 83, which have threaded set screws 84 mounted therein and which engage shaft 75, as shown in Fig. 9. Journalled in said roller bearing 73 is a shaft 75, which has one end thereof connected to flexible coupling 40. The outer end portion of shaft 75 is threaded, and the molded abrasive wheel 76 having the usual bushings 77 thereon is securely mounted on shaft 75 by means of the threaded nut 78.

Numeral 79 designates an elongated horizontal supporting bar which is apertured, and which has one end portion thereof securedby a bolt 80 to one edge portion of the metal base 10. Said bar 79 projects substantially beyond plate 41 and substantially to a point beyond the normal plane of the end face of the abrasive wheel 76 a A metal tool rest 81 in the found a short plate is adjustably mounted a short distance above the projecting end of the bar 79 and normally substantially in a plane just below the plane of the shaft 75. The said tool rest plate 81 is preferably mounted and connected to the bar 79 by a pair of threaded studs 82, said threaded studs threadingly engaging correspondingly spaced threaded holes in said plate 79.

Mourning plate 41 is secured to the collars 32 by means of bolts 43, as previously described, and the abrasive wheel 76 and its shaft and said plate 41 is reciprocated or oscillated in a horizontal path by the mechanism hereinbcfore described. This provides highly advantageous transverse oscillation of the abrasive wheel which prevents excessive abrading, recesses and dot areas on relatively soft and fibrous articles whose faces are to be properly prepared.

Inasmuch as many changes could be made in the foregoing construction, and as many variations could be proposed in the specification and claims without departing from the spirit and scope thereof, it is intended that all matter contained herein shall be considered as illustrative and not in a limiting sense.

I claim:

1. In an oscillating sanding machine, a base; a pair of parallel shafts; journalling brackets secured on said base; said shafts being longitudinally slidable in said brackets;

spring means of the opposite ends of said shafts adapted to press and move said shafts longitudinally; a cross arm connecting intermediate portions of said shafts; a slidably mounted bar connected to said cross arm; a drivable eccentric element mounted on said base; a link connecting outer portion of said bar and the outer portion of said eccentric member whereby reciprocating movement of said link will oscillate said cross arm and said shafts; a mounting frame on'the outer end of the said shafts; journalling members on the opposite ends of said mounting frame; a drum roller journalled on two of said journalling members; the second drum roller journalled on the other of said journalling members, said rollers being adapted to carry an abrasive belt; and means for transmitting rotative power from a prime mover to one of said rollers, said rollers on the forward ends of said shafts being positioned beyond the edge of said base to facilita e the selective engagement of an abrasive belt with work faces, said mounting frame being oscillatable with said shafts.

2. An oscillatable sanding machine substantially as defined in claim 1 and in which said mounting head carries a shoe plate mounted along the path of flight of an abrasive belt, and said shoe plate having a yieldable fiat cushion adapted to be slidably engaged by a movable belt on said pulleys.

3. In an oscillatable abrasive grinder adapted to be selectively lowered and raised with respect to a work surface; -a movable base; a pair of parallel shafts; means on said base for journalling and slidably mounting said shaft; a bar connecting said shafts; a link connected power driven means for reciprocating said link to thereby reciprocate said shafts; springs on the ends of said shafts and engaging said journalling means and adapted to aid in the reciprocating movements of said shafts; a mounting frame on the outer end of said shafts and disposed beyond the edge of said base, said frame having journalling members on the opposite ends thereof; an adjustable shoe mounted on said frame and adapted to be slidably engaged by the lower run of an endless abrasive belt; an idler pulley journalled on the journalling members at one end of 'said mounting frame; a drivable pulley journalled in the journalling members at the other end of said mounting frame; said pulleys being adapted to have an endless abrasive belt mounted thereon; and a power drivable shaft connected to said drivable pulley, the selective vertical movement of said base and parts supported thereon being adapted to selectively engage an abrasive belt on said pulleys with a. work face.

4. In an oscillating sanding machine; a base; a plurality of spaced apart bearing hangers mounted on said base; a plurality of shafts slidable in certain of said hearing hangers; a guide rod slidably mounted in a portion of said bearing hangers; a connecting bar connecting said guide bearing and said shafts; power drivable reciprocating mechanism operatively connected to said guide bar and adapted to transmit movement to reciprocate said shafts and said guide bar; springs mounted on the ends of said shafts for imparting return movements to said shafts; a mounting head connected to the ends of said shafts, said mounting head having adjustable bearing means for journalling an idler pulley, manually adjustable yoke mounted on said head and having aligned bearings therein; a drivable shaft journalled in the bearing of said yoke, said drivable shaft being connectable to a power source; said pulleys being adapted to mount an endless abrasive belt; and means for se-- lectively adjusting the relative angular positions of said head in relation to said reciprocable shafts to provide for varying the path of travel to an abrasive belt on said. pulleys.

5. In a selectively moveable oscillating grinder adapted for driving endless abrasive belts, the base, a first shaft; a second shaft parallel to said first shaft; mounting means is secured to said base and in which said shafts are journaled and slidably mounted; a cross bar connecting said shafts; springs mounted on the ends of said shafts and adapted to return said shafts from power-actuated longitudinal movement of said shafts; an adjustable mounting and journaling head removably secured on the ends of said shafts and normally disposed beyond the edge of said base; said head having two pairs of journaling members; an idler pulley journaled in two of said members; a power driveable pulley journaled on the other pair of said journaling members; said pulleys being adapted to carry an endless abrasive belt; a power transmission shaft journalled on said base; an eccentric element on said last mentioned shaft; a link connected to said cross bar and said eccentric element, the power driven rotation of said last mentioned shaft being adapted to reciprocate and oscillate said cross arm, said first mentioned shaft and said head and pulleys to provide for oscillation of an abrasive belt on said pulleys.

References Cited in the file of this patent UNITED STATES PATENTS 1,862,215 Gallimore June 7, 1932 2,191,155 Mattison Feb. 20, 1940 2,313,254 Mead Mar. 9, 1943 2,573,220 Riedesel et al. Oct. 30, 1951 2,742,741 .Frostad Apr. 24, 1956 FOREIGN PATENTS 20,957 Great Britain Sept. 22, 1911 

